Clothes Washer drain size

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DavidTu, May 14, 2010.

  1. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    I apparently mistakenly sized my clothes washer drain based on dfu's, unaware of the special requirement in UPC calling for a 3" drain. I've seen discussion elsewhere saying that enforcement and interpretation of this vary widely inspector to inspector, region to region. I'm in Seattle WA and wondering how I will likely fare with the inspector.

    Here is the setup: 2" trap & fixture arm going to 2" horzontal drain, which picks up a laundry sink and two lavs before going into a few feet of 3" pipe then 4" pipe on the horizontal and on down the stack.

    Thanks in advance.
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,387
    Location:
    Yakima WA
    From your description, you are just fine. You need a 2" standpipe for new washers which you have and then it increases in size and that too is just fine.
  3. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    That's good to hear Gary... just to be clear, though, the horizontal 2" run (w/ 7 dfu) goes for about a total of 16' horizontal before going to 3" and 4" (horizontal for another 14' or so before vertical). Hope that doesn't change your reply.
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,387
    Location:
    Yakima WA
    So long as you maintain the minimum slope of 1/4" per foot. That is required of every drain regardless of diameter of the pipe.
  5. shacko

    shacko Master Plumber-Gas Fitter

    Messages:
    561
    Location:
    Rosedale, Md
    I hope we have a vent somewhere on your hook-up?
  6. Inspektor Ludwig

    Inspektor Ludwig Journeyman/Inspector

    Messages:
    167
    Location:
    In the good ol' UPC
    Are you wet venting this installation? Curious, what section of chapter 7 UPC are you referencing? I think I know which section you're talking about, the exceptions at the bottom of the DFU table. That language for 6 DFU is for laundrymats and multi-family laundry rooms where you would have a battery of clothes washers draining at the same time. It requires a 3" horizontal drain to address sudsing. Are there Inspectors that require a single family clothes washer to have a 3" drain on the horizontal? Must be Combo Inspectors because I've never heard of any Plumbing Inspector requiring that.
    Last edited: May 16, 2010
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,302
    Location:
    Bothell, Washington
    I think the 3" is an IPC thing on the East Coast.
    I've always used 2" in Seattle.
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